This disclosure relates in general to copier/printers, and more particularly, to cleaning residual toner from an imaging device surface and reducing cleaning blade failure by maintaining a lubricant level to give adequate lubrication.
In a typical electrophotographic printing process, a photoreceptor or photoconductive member is charged to a uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. This process records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. Toner particles attracted from the carrier granules to the latent image form a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. Heating of the toner particles permanently affixes the powder image to the copy sheet. After each transfer process, the toner remaining on the photoconductor is cleaned by a cleaning device.
Blade cleaning is a technique for removing toner and debris from a photoreceptor or photoconductive member. In a typical application, a relatively thin elastomeric blade member is supported adjacent to and transversely across the photoreceptor with a blade edge that chisels or wipes toner from the surface. Toner accumulating adjacent to the blade is transported away from the blade area by a toner transport arrangement or by gravity. Blade cleaning is advantageous over other cleaning systems due to its low cost, small cleaner unit size, low power requirements, and simplicity. However, conventional blade cleaning systems suffer from short life due to failures brought about from interaction with the photoreceptor and toner. The introduction of new blade materials that possess better reliability and enable dramatic life improvements have not been successful. Further, the introduction of photoreceptor surface coatings while improving photoreceptor life typically results in far higher blade wear rates due to friction. Frictional forces cause the blade to stick and slip or chatter as it rubs against the photoreceptor surface. As the blade rubs over the photoreceptor, the blade sticks to the photoreceptor because of static frictional forces. When the sliding friction exceeds static friction, the blade slips over the photoreceptor surface and returns to the resting position. This stick-slip interaction or chatter is a significant cause of blade failure and very disruptive of the printing process.
A lubrication film or lubricating particles between the rubbing surfaces reduces the intensity of the stick-slip (chatter) generated by the relative motion, but adverse interactions with other electrophotographic systems may occur. An analysis of stick-slip behavior as the blade passes over a photoreceptor shows a low frequency once-around strain signature experienced by the blade that is independent of the speed of the photoreceptor. At very low speeds, a higher frequency, lower amplitude strain is observed on top of the low frequency once-around strain signature. This higher frequency strain was associated with stick-slip behavior of the blade tip. Whenever the higher frequency strain was observed, an audible stick-slip sound was also heard.
A conventional remedial practice is the use of a toner lubrication stripe. The expectation is that the toner lubrication stripe would provide improved blade lubrication as long as there was an amount of toner riding in front of the blade. Another remedial practice is the application of lubrications stripes consisting of lubricants other than toner. These other lubricants may include PMMA, zinc stearate or other stearates, Unilin or other waxes, PTFE or other low surface energy lubricant particles compatible with the electrophotographic system. The lubrication stripe is introduced in the interdocument zone at every predetermined number of prints or cycles. The interdocument zone is typically in a fixed, stationary location on the photoreceptor so that the lubrication stripes are always developed on the same spot. The development frequency of lubrication stripes is also typically fixed, but various schemes have been proposed over the years to develop stripes based on the need for lubrication.
The current lubrication stripe schemes have not significantly improved blade life because of a failure to provide uniform lubrication. Instead of providing uniform improved blade lubrication and lower blade strain, the lubrication effect was evident only at the original location of the lubrication stripe. Even after numerous drum cycles the lubrication remained localized to the original deposit spot and only slowly spread in the process direction. The accumulated lubricant in front of the blade had no apparent effect on cleaning blade strain reduction. The reduction in chatter was localized to the segment of the drum near the lubrication stripe and is not instantly smeared everywhere.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification there is need in the art for systems, apparatus, and/or methods that increases the reliability of cleaning blades while minimizing lubricant usage.